US11581369B2 - Semiconductor switch element and method of manufacturing the same - Google Patents

Semiconductor switch element and method of manufacturing the same Download PDF

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US11581369B2
US11581369B2 US17/117,576 US202017117576A US11581369B2 US 11581369 B2 US11581369 B2 US 11581369B2 US 202017117576 A US202017117576 A US 202017117576A US 11581369 B2 US11581369 B2 US 11581369B2
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substrate
trench
transistor device
switch element
semiconductor switch
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US20210183948A1 (en
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Sylvain Leomant
Gerhard Noebauer
Thomas Oszinda
Christian Gruber
Sergey ANANIEV
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Infineon Technologies Austria AG
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Infineon Technologies Austria AG
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10B—ELECTRONIC MEMORY DEVICES
    • H10B63/00—Resistance change memory devices, e.g. resistive RAM [ReRAM] devices
    • H10B63/30—Resistance change memory devices, e.g. resistive RAM [ReRAM] devices comprising selection components having three or more electrodes, e.g. transistors
    • H10B63/34—Resistance change memory devices, e.g. resistive RAM [ReRAM] devices comprising selection components having three or more electrodes, e.g. transistors of the vertical channel field-effect transistor type
    • H01L27/2454—
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
    • H01L21/77—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate
    • H01L21/78—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices
    • H01L21/82—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices to produce devices, e.g. integrated circuits, each consisting of a plurality of components
    • H01L21/822—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices to produce devices, e.g. integrated circuits, each consisting of a plurality of components the substrate being a semiconductor, using silicon technology
    • H01L21/8232—Field-effect technology
    • H01L21/8234—MIS technology, i.e. integration processes of field effect transistors of the conductor-insulator-semiconductor type
    • H01L21/823475—MIS technology, i.e. integration processes of field effect transistors of the conductor-insulator-semiconductor type interconnection or wiring or contact manufacturing related aspects
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
    • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
    • H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
    • H01L21/76838—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
    • H01L21/76877—Filling of holes, grooves or trenches, e.g. vias, with conductive material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
    • H01L21/77—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate
    • H01L21/78—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices
    • H01L21/82—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices to produce devices, e.g. integrated circuits, each consisting of a plurality of components
    • H01L21/822—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices to produce devices, e.g. integrated circuits, each consisting of a plurality of components the substrate being a semiconductor, using silicon technology
    • H01L21/8232—Field-effect technology
    • H01L21/8234—MIS technology, i.e. integration processes of field effect transistors of the conductor-insulator-semiconductor type
    • H01L21/823487—MIS technology, i.e. integration processes of field effect transistors of the conductor-insulator-semiconductor type with a particular manufacturing method of vertical transistor structures, i.e. with channel vertical to the substrate surface
    • H—ELECTRICITY
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    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/02—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers
    • H01L27/04—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers the substrate being a semiconductor body
    • H01L27/08—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers the substrate being a semiconductor body including only semiconductor components of a single kind
    • H01L27/085—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers the substrate being a semiconductor body including only semiconductor components of a single kind including field-effect components only
    • H01L27/088—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers the substrate being a semiconductor body including only semiconductor components of a single kind including field-effect components only the components being field-effect transistors with insulated gate
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/40—Electrodes ; Multistep manufacturing processes therefor
    • H01L29/401—Multistep manufacturing processes
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    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/40—Electrodes ; Multistep manufacturing processes therefor
    • H01L29/402—Field plates
    • H01L29/407—Recessed field plates, e.g. trench field plates, buried field plates
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    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/40—Electrodes ; Multistep manufacturing processes therefor
    • H01L29/41—Electrodes ; Multistep manufacturing processes therefor characterised by their shape, relative sizes or dispositions
    • H01L29/417—Electrodes ; Multistep manufacturing processes therefor characterised by their shape, relative sizes or dispositions carrying the current to be rectified, amplified or switched
    • H01L29/41725—Source or drain electrodes for field effect devices
    • H01L29/41741—Source or drain electrodes for field effect devices for vertical or pseudo-vertical devices
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
    • H01L29/66007—Multistep manufacturing processes
    • H01L29/66075—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials
    • H01L29/66227—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials the devices being controllable only by the electric current supplied or the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched, e.g. three-terminal devices
    • H01L29/66409—Unipolar field-effect transistors
    • H01L29/66477—Unipolar field-effect transistors with an insulated gate, i.e. MISFET
    • H01L29/66666—Vertical transistors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
    • H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
    • H01L29/76—Unipolar devices, e.g. field effect transistors
    • H01L29/772—Field effect transistors
    • H01L29/78—Field effect transistors with field effect produced by an insulated gate
    • H01L29/7801—DMOS transistors, i.e. MISFETs with a channel accommodating body or base region adjoining a drain drift region
    • H01L29/7802—Vertical DMOS transistors, i.e. VDMOS transistors
    • H01L29/7813—Vertical DMOS transistors, i.e. VDMOS transistors with trench gate electrode, e.g. UMOS transistors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
    • H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
    • H01L29/76—Unipolar devices, e.g. field effect transistors
    • H01L29/772—Field effect transistors
    • H01L29/78—Field effect transistors with field effect produced by an insulated gate
    • H01L29/7827—Vertical transistors
    • H—ELECTRICITY
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    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/40—Electrodes ; Multistep manufacturing processes therefor
    • H01L29/41—Electrodes ; Multistep manufacturing processes therefor characterised by their shape, relative sizes or dispositions
    • H01L29/417—Electrodes ; Multistep manufacturing processes therefor characterised by their shape, relative sizes or dispositions carrying the current to be rectified, amplified or switched
    • H01L29/41725—Source or drain electrodes for field effect devices
    • H01L29/41766—Source or drain electrodes for field effect devices with at least part of the source or drain electrode having contact below the semiconductor surface, e.g. the source or drain electrode formed at least partially in a groove or with inclusions of conductor inside the semiconductor

Definitions

  • the present disclosure relates to a semiconductor switch element with vertical transistor devices.
  • a vertical channel region is formed in the body region of the device.
  • the gate region is arranged laterally aside, it comprises a gate interlayer dielectric and a gate electrode. By applying a voltage to the gate electrode, the channel formation in the channel region can be controlled.
  • the source and the drain region of the device can be arranged at opposite sides of the semiconductor substrate, for instance the source region at a front side and the drain region at a back side of the substrate.
  • the switch element comprises a first vertical transistor device and a second vertical transistor device formed in the same substrate.
  • the source regions of the transistor devices are arranged on a first side of the substrate, and the drain regions are formed vertically opposite on a second side of the substrate.
  • the drain regions are connected with each other by a conductive element which is arranged on the second side of the substrate.
  • a trench is formed on the second side of the substrate, and at least a part of the conductive element is arranged in this trench.
  • the conductive material By forming the conductive element in the trench, the conductive material can be arranged closer to the active region of the respective device, e.g. closer to the drift region.
  • the “effective thickness” of the substrate can be reduced in terms of the electric resistance, and a lower resistivity can for instance reduce conduction losses.
  • the switch element with the transistor devices which are arranged in this common drain or “back-to-back” configuration, can for instance be used in a battery management system, wherein the reduced conduction losses can allow for higher charging currents.
  • the same “effective thickness” would be realized without the trench structure by a homogeneous back side grinding, the remaining substrate thickness would be so small that an excessive wafer bow would result.
  • the wafer bow which can for instance result from the mismatch in the thermal expansion of the substrate and the metal and can depend on the substrate and metal thickness, could cause handling problems, e. g. in the subsequent backend processing.
  • the trench is a recess which extends into the substrate to a bottom of the trench. Laterally, it is defined by the sidewalls of the trench. Perpendicularly to such a cross-section, the trench can for instance have an elongated shape, or it can have a hole-like shape, see in detail below.
  • the conductive element can be formed of any conductive material, like for instance doped polysilicon.
  • the conductive material can be a metal material, e. g. copper, in particular a copper-based alloy.
  • the entire conductive element could be arranged in the trench, for instance in case of a single longitudinal trench connecting the transistor devices.
  • only a part of the conductive element can be arranged in the trench, other parts of the conductive element being arranged in other trenches and/or on the surface of the substrate, namely on the second side thereof.
  • a conductive element extending partially on the surface of the substrate can be combined with longitudinal trenches or hole-shaped trenches. In case of hole-shaped trenches, the part of the conductive element arranged on the surface can connect the transistor devices laterally.
  • the source and the drain region of a respective transistor device can be of a first conductivity type, its body region being of a second conductivity type opposite to the first conductivity type.
  • the first conductivity type is n-type and the second conductivity type is p-type.
  • the vertical transistor devices are formed in the same substrate, which can enable a small footprint and low profile package thus (particularly advantageous in e. g. handheld applications).
  • the substrate can for instance be formed by the initial wafer material, for example silicon wafer material, e. g. together with one or more epitaxial layers. In the latter, the source and the body regions can be formed.
  • the substrate is formed of the semiconducting layer(s) of the switch element, which can be or is/are doped.
  • Each transistor device can comprise a plurality of transistor cells, which have a common source contact, a common drain contact and a common gate contact.
  • the first and the second transistor device can respectively have an individual gate contact. In other words, the first and the second transistor device can be switched independently of each other.
  • the “vertical” direction lies perpendicular to a surface of the substrate, for instance a surface of the silicon wafer material and/or a surface of an epitaxial layer.
  • the first and the second side of the substrate lie opposite to each other with respect to the vertical direction.
  • the lateral directions lie perpendicular to the vertical direction, the die area is for instance taken laterally.
  • the trench formed at the second side of the substrate extends vertically into the substrate.
  • the trench has a vertical depth of 15 ⁇ m at minimum, in particular 20 ⁇ m at minimum.
  • Possible upper limits of the trench depth can for instance be 40 ⁇ m at maximum, in particular 35 ⁇ m at maximum. In this range, a trade-off between for instance a reduction of the remaining effective thickness and an acceptable mechanical stress in the substrate can be achieved.
  • a respective transistor device can comprise a drift region.
  • the drift region and the drain region both are of the first conductivity type, for instance n-type, wherein the doping concentration is lower in the drift region.
  • the conductive element or material in the trench it can be brought rather close to the drift region, which lowers the resistivity.
  • the vertical distance between a bottom of the trench and the drift region is 30 ⁇ m at maximum, further upper limits being 25 ⁇ m, 20 ⁇ m or 15 ⁇ m at maximum. Possible lower limits of the vertical distance can for instance be 5 ⁇ m or 10 ⁇ m.
  • the trench has a lateral width of 100 ⁇ m at maximum, further upper limits being for instance 80 ⁇ m, 60 ⁇ m, 50 ⁇ m or 40 ⁇ m at maximum. Possible lower limits of the lateral width can for instance be 15 ⁇ m or 20 ⁇ m at minimum.
  • the width is taken at the vertically outer end of the trench, opposite to the bottom of the trench. In particular, the width can be taken in a second lateral direction perpendicular to a first lateral direction (in the first lateral direction, the transistor devices are arranged laterally aside each other, see below).
  • the trench can be filled completely with the conductive material of the conductive element.
  • the conductive material fills only a portion of the trench, wherein no conductive material is arranged in another portion of the trench.
  • the conductive material can cover the bottom and/or sidewalls of the trench, leaving, in a cross-sectional view, a central portion without conductive material.
  • the partial filling of the trench can for instance reduce the mechanical stress in the substrate, as the conductive material, in particular metal, can have more free space to relax.
  • the other portion of the trench which is not filled with conductive material, is filled with a polymeric material.
  • the conductive material and the polymeric material can fill up the trench completely.
  • the polymeric material filler can be an epoxy material, for example an epoxy resin.
  • the transistor devices could be connected by a single longitudinal trench.
  • a plurality of trenches are formed on the second side of the substrate, wherein a part of the conductive element is arranged in each of the trenches. Compared to the single trench solution, this can for instance enable a more even distribution of the mechanical stress in the substrate.
  • the trenches are arranged laterally aside each other in a second lateral direction.
  • the transistor devices lie laterally aside each other, wherein the second lateral direction lies perpendicular thereto.
  • the trenches arranged aside each other can be longitudinal trenches (see FIG. 1 A ) or hole-shaped trenches (see FIG. 4 ).
  • a plurality of hole-shaped trenches are formed on the second side of the substrate.
  • the conductive material can for instance have columnar shape, in particular a hollow columnar shape in case of the partial filling described above.
  • Providing hole-shaped trenches can also allow for an even distribution of the wafer bow in both, the first and the second lateral direction.
  • a first subset of the hole-shaped trenches is arranged vertically aligned with the first transistor device, and a second subset of the hole-shaped trenches is arranged vertically aligned with the second transistor device.
  • the current can be collected from the drain region of the first transistor device, and via the second subset, the current can be collected from the drain region of the second transistor device.
  • the first subset of trenches reduces the effective substrate thickness at the first transistor device
  • the second subset of trenches reduces the effective thickness at the second transistor device.
  • the hole-shaped trenches can be arranged in rows. In each row, some of the trenches can be aligned, in particular on a straight line respectively. The rows are arranged laterally aside each other, e. g. basically parallel to each other. In an embodiment, the hole-shaped trenches of neighbouring rows are arranged with an offset to each other. In other words, along the row direction, the hole-shaped trenches are arranged alternately in one of the two neighbouring rows respectively.
  • the mechanical stress in the substrate can depend on the distance between neighbouring trenches, namely increase with decreasing distance. Provided that the distance between neighbouring trenches remains unchanged, the offset can allow for a denser packing (e. g. up to 15%) of the hole-shaped trenches and a lower resistivity without increasing the mechanical stress in the substrate.
  • the offset trenches can for instance be arranged in a hexagonal pattern, e. g. a honeycomb pattern.
  • a hole-shaped trench can basically have any cross-section, for instance a polygonal cross-section, e. g. rectangular (possibly with rounded edges).
  • a respective hole-shaped trench has a circular cross-section. This can allow for a dense packing of the trenches and/or a reduction of the mechanical stress in the substrate due to the round shape.
  • the trench is a longitudinal trench and extends laterally from the first to the second transistor device.
  • a middle section of the longitudinal trench can be arranged laterally between the transistor devices, and the end sections of the trench can lie vertically aligned with one of the transistor devices respectively.
  • the trenches can extend parallelly to each other.
  • longitudinal and hole-shaped trenches can be combined in the same switch element.
  • the switch element can be provided either with hole-shaped trenches or with one or more longitudinal trenches.
  • the application also relates to a switch device which comprises the semiconductor switch element disclosed here and a board, on which the semiconductor switch element is mounted.
  • the board can be a circuit board, for instance a printed circuit board.
  • the switch element can be mounted on the board by flip chip bonding, namely with the first side of the substrate facing the board.
  • metal pads forming source contacts and/or gate contacts can be provided, and these pads can be soldered directly to the board.
  • this polymeric material can cover the second side of the substrate entirely, providing a certain protection.
  • the invention also relates to a method of manufacturing a switch element disclosed here, comprising the steps:
  • the invention also relates to a use or method of using a semiconductor switch element, or respective switch device, in a battery management system.
  • a battery management system can for instance ensure that a rechargeable battery remains in safe operating area while avoiding over-current and/or over-voltage stresses.
  • the switch element or device of this disclosure can be used for connecting and disconnecting the battery to or from a charge or discharge path. With the bidirectional switch element or switch device of the present application, it is possible to allow or block the current flow in both directions.
  • an approach of this application is to arrange the drain contact or metallization of a vertical transistor device in a trench. This can also be advantageous independently of connecting two devices formed in the same substrate, namely reduce the drain contact resistivity while maintaining at least some structural integrity of the substrate (e.g. advantageous in view of the wafer bow, see above).
  • a semiconductor transistor device formed in a substrate, having a source region formed on a first side of the substrate, a drain region formed on a second side of the substrate, vertically opposite to the first side, and a drain metallization arranged on the second side of the substrate, electrically contacting the drain region, wherein a trench extending vertically into the substrate is formed on the second side of the substrate, and wherein at least a part of the drain metallization is arranged in the trench.
  • FIG. 1 A shows a semiconductor switch element with a first and a second transistor device formed in the same substrate
  • FIG. 1 B shows a detailed view of a transistor device of the switch element of FIG. 1 A ;
  • FIG. 2 A illustrates the switch element of FIG. 1 A in a cross-sectional view perpendicular to the sectional plane of FIG. 1 A ;
  • FIG. 2 B illustrates an alternative switch element with the trenches filled only partly
  • FIG. 3 illustrates a further alternative switch element with the trenches filled additionally with a polymeric material
  • FIG. 4 shows a schematic top view of a switch element and illustrates hole-shaped trenches arranged with an offset
  • FIG. 5 shows a vertical cross-sectional view of a switch device with a switch element mounted on a board
  • FIGS. 6 A- 6 D illustrate the manufacturing of the switch element of FIG. 2 B with trenches formed in the substrate
  • FIGS. 7 A- 7 D illustrate the manufacturing of the switch element of FIG. 3 ;
  • FIG. 8 illustrates some manufacturing steps in a flow diagram.
  • FIG. 1 A shows a semiconductor switch element 10 comprising a first vertical transistor device 1 . 1 and a second vertical transistor device 1 . 2 .
  • the transistor devices 1 . 1 , 1 . 2 are formed in the same substrate 8 .
  • a source region 2 . 1 of the first transistor device 1 . 1 and a source region 2 . 2 of the second transistor device 1 . 2 are arranged.
  • a drain region 4 . 1 of the first transistor device 1 . 1 and a drain region 4 . 2 of the second transistor device 1 . 2 are arranged.
  • a conductive element 9 is formed on the second side 8 . 2 of the substrate 8 . It electrically connects the drain region 4 . 1 of the first transistor device 1 . 1 and the drain region 4 . 2 of the second transistor device 1 . 2 .
  • a trench 11 extends vertically into the substrate 8 , and a part 9 . 1 of the conductive element 9 is arranged in the trench 11 .
  • a vertical distance 23 between the conductive element 9 at a bottom 15 of the trench 11 and a respective drift region 13 . 1 , 13 . 2 of the respective transistor device 1 . 1 , 1 . 2 can be reduced (e. g. to around 10 ⁇ m). In consequence, the electrical resistivity is reduced, see the description above in detail.
  • FIG. 1 B shows an enlarged view of a transistor cell.
  • the first and the second transistor 1 . 1 , 1 . 2 have an identical layout, the following description applies for both of them.
  • the body region 6 . 1 , 6 . 2 is arranged.
  • a gate region 5 . 1 , 5 . 2 is formed, it comprises a gate electrode 70 . 1 , 70 . 2 and a gate dielectric 71 . 1 , 71 . 2 .
  • a voltage to the gate electrode 70 . 1 , 70 . 2 By applying a voltage to the gate electrode 70 . 1 , 70 . 2 , a channel formation in the body region 6 . 1 , 6 . 2 can be controlled.
  • the gate region 5 . 1 , 5 . 2 is arranged in a gate trench 72 . 1 , 72 . 2 .
  • a field plate 73 . 1 , 73 . 2 is formed in the gate trench 72 . 1 , 72 . 2 below the gate electrode 70 . 1 , 70 . 2 , electrically isolated therefrom.
  • the electrical contact of the gate electrode 70 . 1 , 70 . 2 on the first side 8 . 1 of the substrate 8 is not visible (it is arranged in front of or behind the drawing plane).
  • a contact plug 76 . 1 , 76 . 2 connects the contact pad 75 . 1 , 75 . 2 to the source and body region 2 . 1 , 2 . 2 , 6 . 1 , 6 . 2 .
  • FIG. 2 A shows the switch element 10 of FIG. 1 A in another sectional plane, perpendicular to the sectional plane of FIG. 1 A .
  • the trenches 11 are longitudinal trenches 21 which extend in a first vertical direction 41 from the first transistor device 1 . 1 to the second transistor device 1 . 2 ( FIG. 1 A ).
  • the trenches 11 , 21 are arranged laterally aside each other ( FIG. 2 A ).
  • the resistivity and switching losses thus, can be reduced.
  • the silicon material remains between the trenches 11 , 21 . Consequently, a wafer bow resulting from the mismatch in the thermal expansion of silicon and metal is lower compared to a solution obtained by grinding the entire second side 8 . 2 down to the vertical distance 23 .
  • the trenches 11 , 21 respectively have a lateral width 30 of around 30 ⁇ m.
  • a lateral distance 31 in between the trenches 11 , 21 is around 30 ⁇ m in this example.
  • the trenches 11 , 21 have a depth 22 of around 35 ⁇ m.
  • FIG. 2 B differs from FIG. 2 A in that the conductive material of the conductive element 9 fills only a respective portion 11 . 1 of a respective trench 11 . In another portion 11 . 2 of the respective trench 11 , no conductive material is arranged. Likewise, more space to relax is left for the conductive material, e. g. metal, which can reduce the mechanical stress in the substrate 8 .
  • the conductive material e. g. metal
  • FIG. 3 differs from FIG. 2 B in that the other portion 11 . 2 of the respective trench 11 is filled up with a polymeric material 35 .
  • the polymeric material 35 can for instance be an epoxy resin, it can cover the second side 8 . 2 of the substrate 8 partly or entirely. It can provide a protection against humidity and the like.
  • FIG. 4 shows a schematic top view of a switch element 10 comprising a first transistor device 1 . 1 and a second transistor device 1 . 2 formed in the same substrate 8 .
  • the first and the second transistor device 1 . 1 , 1 . 2 are connected by a conductive element (not shown in FIG. 4 ).
  • the conductive element is arranged in trenches 11 , namely hole-shaped trenches 51 in this embodiment.
  • the hole-shaped trenches 51 can have the same design as the trenches 11 shown in FIGS. 2 A, 2 B and 3 . They can be filled entirely or partly with the conductive material, optionally in combination with a polymeric material.
  • the hole-shaped trenches 51 . 1 , 51 . 2 for both transistor devices 1 . 1 , 1 . 2 are arranged in rows 55 .
  • the hole-shaped trenches 51 of neighbouring rows 55 . 1 , 55 . 2 are arranged with an offset 56 to each other.
  • the packing density of the hole-shaped trenches 51 can be increased without reducing the minimum distance between neighbouring hole-shaped trenches 51 .
  • FIG. 5 shows a switch device 60 comprising a switch element 10 as described above and a board 61 .
  • the switch element 10 is mounted on the board 61 by flip chip bonding, the first side 8 . 1 of the substrate 8 faces the board 61 .
  • the electrical contact to the board 61 is formed via the contact pads 75 . 1 , 75 . 2 , these are soldered directly to the board 61 (not shown in detail).
  • FIGS. 6 A-D illustrate some manufacturing steps for the switch element 10 of FIG. 2 B .
  • a hard mask 80 is deposited on the second side 8 . 2 of the substrate 8 and structured.
  • the hard mask 8 defines the locations 81 where the trenches 11 are etched ( FIG. 6 A ).
  • a seed layer 82 is deposited ( FIG. 6 B ), for instance by sputtering.
  • a photoresist mask 83 is deposited and structured.
  • the photoresist mask 83 defines the location for the metal deposition in the subsequent plating process ( FIG. 6 C ), for instance copper plating.
  • the photoresist mask 83 is removed, leaving the conductive element 9 formed in the plating process ( FIG. 6 D ).
  • the part of the seed layer 82 aside the conductive element 9 can be removed in a brief etch step.
  • FIGS. 7 A-D illustrate some manufacturing steps for the switch element 10 of FIG. 3 .
  • the metal plating is applied without a photoresist mask
  • the conductive material 90 covers the entire second side 8 . 2 of the substrate 8 ( FIG. 7 A ).
  • the polymeric material 35 is deposited, filling the remaining holes in the trenches 11 ( FIG. 7 B ).
  • the polymeric material 35 is structured ( FIG. 7 C ) and used as a mask for the removal of the conductive material 90 arranged laterally at the side ( FIG. 7 D ).
  • the polymeric material 35 remains in the trenches 11 .
  • the switch element 10 of FIG. 2 B could be obtained by removing the polymeric material 35 subsequently.
  • a photoresist could be used in the steps of FIGS. 7 A-D instead of the polymeric material.
  • FIG. 8 illustrates some manufacturing steps in a flow diagram 95 .
  • the trench 11 is etched 92 into the substrate 8 .
  • the trench 11 is filled 93 at least partly with the conductive material to form the conductive element 9 .

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JP2010103208A (ja) * 2008-10-22 2010-05-06 Denso Corp 半導体装置
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KR20210075019A (ko) 2021-06-22

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